1. Field of the Invention
This invention relates to a method for polishing a wafer and a wafer produced by this method, and more particularly to a method for polishing a wafer, which is capable of reducing particles existing on an end face of the wafer with few step number.
2. Description of the Related Art
In the conventional wafer production, after a wafer is cut out from a single crystal ingot at a slicing step, at least one of both surfaces of the wafer is subjected to a mirror polishing step. For the purpose of removing particles from an end face of the wafer and improving a strength thereof, it is common to conduct a preliminary mirror polishing for finish beveling the end face of the wafer before the above mirror polishing step of the at least one surface (see JP-A-H11-188589 and WO 2005/055302).
When a wafer is produced by the above-mentioned method, as shown, for example, in FIG. 1, a polishing apparatus 100 used in the mirror polishing step of the at least one surface, e.g. front surface of a semiconductor wafer 101 is provided with a resin guide 102 for preventing the wafer from jumping out. However, when a rear surface of the wafer is mirror-polished by the polishing apparatus 100, the wafer is moved in a horizontal direction to repeatedly strike on the resin guide 102, so that there is a fear of causing scratches on the end face of the wafer. Also, a polishing slurry used in the mirror polishing step of the rear surface of the wafer enters into a space S between the end face of the wafer and the guide 102, and adheres to the end face of the wafer resulting in a problem that many particles are existent on the end face.
FIG. 2 is a schematic view showing an example of the slurry adhered to the end face of the wafer, wherein FIG. 2(a) is a view for explaining an observing direction 201 to a wafer 200 and FIG. 2(b) is a partial schematic view showing an end face 202 of the wafer 200 inclined by 45° from a standard face toward a front surface 200a viewing from the observing direction 201. As shown in FIG. 2(b), an adhered slurry aggregate (particles) 203 is existent on the end face 202 of the wafer 200. It is anticipated that this phenomenon would have a significantly bad influence on a wafer having a diameter of not less than 450 mm.